A system and method of altering frames being processed by a network processing unit. The system includes a set of defined alterations, with some of the alterations being fixed alterations which are advantageously handled by hardware to accomplish the fixed alterations rapidly and without executing a stored program and other alterations which include a variable portion, with these variable alterations being accomplished through the use of stored programs allowing the variables to be used to effect variable alterations to a frame. The present system accommodates a change in the duration of life of a frame or information unit and addition or deletion of bits and also allows for a new cyclic redundancy checking to be accomplished for a revised information unit. Advantageously, the frame alteration system is on the same substrate as the processors.